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Moradi, M., Oskooi, B., Pushkarev, P., Smirnov, M. & Esmaeili Oghaz, H. (2019). Cooperative inversion of magnetotelluric and seismic data on Shurab diapirs in Central Iran. Environmental Earth Sciences, 78(11), Article ID 341.
Open this publication in new window or tab >>Cooperative inversion of magnetotelluric and seismic data on Shurab diapirs in Central Iran
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2019 (English)In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 78, no 11, article id 341Article in journal (Refereed) Published
Abstract [en]

Using diapirs as liquid or gas storage structures has increased because salt formations are considered to be extremely impermeable and non-reactive. The process of delineating the diapirs' structures ends in lots of challenges due to their geological complexity. Therefore, the integration of different geophysical methods seems to be necessary to cover different physical characteristics of the diapirs. Shurab diapirs located at the NW of Kashan in Qom basin of Central Iran have been considered as candidates for the first natural gas storages in Iran. A previous 2D seismic survey across the diapir No. 4 of Shurab could not resolve the diapir structure properly and some ambiguities left unresolved. The main goal of this paper is to resolve the structure of diapir No. 4 by employing a cooperative inversion of the seismic and magnetotelluric (MT) data and a comparison with the joint inversion of transverse electric (TE) and transverse magnetic (TM) modes of the MT data. Both inversion schemes show the salt and sedimentary sequences of the stratigraphy of the Qom basin. The sequences of formations from the surface to depth are classified as upper red formation (URF), Qom formation (QF) and lower red formation (LRF). The results also show that the salt body has originated from the LRF. It is worthwhile to mention that the results from the cooperative inversion provide more details especially on the flanks and overhangs of the diapir No. 4. In addition, we have come to the conclusion that the right lateral strike-slip fault system is the most responsible phenomenon for the development of the diapirs in the survey area and the Sen-Sen fault plays a basic role as an elevator to pushing the salt up. The results are in good agreements with the resistivity and density logs of the boreholes. Moreover, the information from the geology, the cooperative inversion results on diapir No. 4, and the coincidence of the path of the Sen-Sen fault with the outcrops of the diapirs No. 1, 3 and 4 obviously provide that the tectonic scenario of the existence for diapir No. 4 could be appointed to the diapirs No. 1 and 3 equally. Another probable consequence would be the under surface continuation of the salt bodies all along the Sen-Sen fault, the verification of which requires regional MT surveys in a regular grid.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Cooperative inversion, Magnetotelluric (MT), Seismic, Shurab diapirs, Qom basin
National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-74895 (URN)10.1007/s12665-019-8342-9 (DOI)000469817700002 ()2-s2.0-85066465823 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-24 (johcin)

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24Bibliographically approved
Oskooi, B., Moradi, M. & Smirnov, M. (2019). Integrated interpretation of seismic and magnetotelluric data on Shurab diapirs in Qom basin, Central Iran. Acta Geophysica, 67(4), 1071-1090
Open this publication in new window or tab >>Integrated interpretation of seismic and magnetotelluric data on Shurab diapirs in Qom basin, Central Iran
2019 (English)In: Acta Geophysica, ISSN 1895-6572, E-ISSN 1895-7455, Vol. 67, no 4, p. 1071-1090Article in journal (Refereed) Published
Abstract [en]

In recent decades, diapirs are frequently used for CO2 and natural gas storage due to their extremely impermeable and non-reactive characteristics. Among various approaches, we use an integrated interpretation approach to resolve the diapir no. 4 belonging to the Shurab diapirs (SD). The SD is a group of diapirs that have pierced to the surface of the Qom basin of Central Iran, which is a candidate for natural gas storages. The complex geology of the SD is the main cause that previous 2D seismic surveys across the diapir could not provide required information to propose any location for any exploration borehole. Consequentially, 28 magnetotelluric (MT) and 1 audio-magnetotelluric station were measured along a SW-NE profile. Dimensionality and strike analysis for all stations is done by the use of phase tensor analysis. We used the nonlinear conjugate gradient algorithm to invert the TE- and TM-modes data simultaneously in 2D. The resistivity model was compared with the interpreted results of the post-stack depth migration model using seismic attributes. In order to extract the determinative geological information from the low-quality seismic section, envelope, variance, sweetness and instantaneous frequencies attributes were used. The integrated interpretation of the seismic and MT data resolves a precise geometry of the salt body, location of the dense part of the diapir as well as the tectonics around the diapir. The integrated interpretation of seismic and MT data of diapir no. 4 resulted in an exploration drilling program.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Integrated interpretation, Magnetotelluric, Natural gas storage, Qom basin, Shurab diapirs, seismic
National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-74962 (URN)10.1007/s11600-019-00286-2 (DOI)000476529200005 ()2-s2.0-85065550470 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-19 (johcin)

Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-08-19Bibliographically approved
Cherevatova, M., Egbert, G. D. & Smirnov, M. Y. (2018). A multi-resolution approach to electromagnetic modelling. Geophysical Journal International, 214(1), 656-671
Open this publication in new window or tab >>A multi-resolution approach to electromagnetic modelling
2018 (English)In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 214, no 1, p. 656-671Article in journal (Refereed) Published
Abstract [en]

We present a multi-resolution approach for 3-D magnetotelluric forward modelling. Our approach is motivated by the fact that fine-grid resolution is typically required at shallow levels to adequately represent near surface inhomogeneities, topography and bathymetry, while a much coarser grid may be adequate at depth where the diffusively propagating electromagnetic fields are much smoother. With a conventional structured finite difference grid, the fine discretization required to adequately represent rapid variations near the surface is continued to all depths, resulting in higher computational costs. Increasing the computational efficiency of the forward modelling is especially important for solving regularized inversion problems. We implement a multi-resolution finite difference scheme that allows us to decrease the horizontal grid resolution with depth, as is done with vertical discretization. In our implementation, the multi-resolution grid is represented as a vertical stack of subgrids, with each subgrid being a standard Cartesian tensor product staggered grid. Thus, our approach is similar to the octree discretization previously used for electromagnetic modelling, but simpler in that we allow refinement only with depth. The major difficulty arose in deriving the forward modelling operators on interfaces between adjacent subgrids. We considered three ways of handling the interface layers and suggest a preferable one, which results in similar accuracy as the staggered grid solution, while retaining the symmetry of coefficient matrix. A comparison between multi-resolution and staggered solvers for various models shows that multi-resolution approach improves on computational efficiency without compromising the accuracy of the solution.

Place, publisher, year, edition, pages
Oxford University Press, 2018
Keywords
Electromagnetic theory, Numerical modeling, Magnetotellurics
National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-69293 (URN)10.1093/gji/ggy153 (DOI)000448235200044 ()
Note

Validerad;2018;Nivå 2;2018-06-11 (rokbeg)

Available from: 2018-06-11 Created: 2018-06-11 Last updated: 2018-11-15Bibliographically approved
Oskooi, B., Parnow, S., Smirnov, M., Varfinezhad, R. & Yari, M. (2018). Attenuation of random noise in GPR data by image processing. Arabian Journal of Geosciences, 11(21), Article ID 677.
Open this publication in new window or tab >>Attenuation of random noise in GPR data by image processing
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2018 (English)In: Arabian Journal of Geosciences, ISSN 1866-7511, E-ISSN 1866-7538, Vol. 11, no 21, article id 677Article in journal (Refereed) Published
Abstract [en]

Random noise in ground penetrating radar (GPR) data affects the signal-to-noise ratio, blurs the details, and complicates reconnaissance of the useful information. Many methods with different advantages and disadvantages have been proposed to eliminate or weaken the random noise. We have reviewed basic principles of various signal processing techniques including the curvelet transform (CT), non-local mean (NLM), median, and mean filters to remove the random noise and compared their performances using synthetic and actual GPR data. The performances of the four filters were analyzed on synthetic GPR data both in time and frequency domains. On noisy synthetic data, results indicate that the CT filter performs better than NLM, mean, and median filters at attenuating random noise and improving S/N of the GPR data. On the real data, the performance of only the NLM and CT filters was investigated. Comparing the results clearly shows the CT filter robustness for the random noise attenuation and simultaneously its signal preservation

Place, publisher, year, edition, pages
Heidelberg: Springer, 2018
Keywords
Curvelet transform, GPR, Mean filter, Median filter, Non-local mean, Random noise
National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-71857 (URN)10.1007/s12517-018-4035-z (DOI)000449698200008 ()2-s2.0-85056234003 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-12-03 (inah)

Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-09-13Bibliographically approved
Paembonan, A. Y., Arjwech, R., Davydycheva, S. N., Smirnov, M. & Strack, K. M. (2017). An application of LOTEM around salt dome near Houston, Texas. Paper presented at 1st International Geo-Electromagnetic Workshop 2017, IGeo-EM 2017, Campus of Institute Technology of BandungBandung, West Java, Indonesia, 21-24 February 2017. AIP Conference Proceedings, 1861, Article ID 030006.
Open this publication in new window or tab >>An application of LOTEM around salt dome near Houston, Texas
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2017 (English)In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1861, article id 030006Article in journal (Refereed) Published
Abstract [en]

A salt dome is an important large geologic structure for hydrocarbon exploration. It may seal a porous reservoir of rocks that form petroleum reservoirs. Several techniques such as seismic, gravity, and electromagnetic including magnetotelluric have successfully yielded salt dome interpretation. Seismic has difficulties seeing through the salt because the seismic energy gets trapped by the salt due to its high velocity. Gravity and electromagnetics are more ideal methods. Long Offset Transient Electromagnetic (LOTEM) and Focused Source Electromagnetic (FSEM) were tested over a salt dome near Houston, Texas. LOTEM data were recorded at several stations with varying offset, and the FSEM tests were also made at some receiver locations near a suspected salt overhang. The data were processed using KMS's processing software: First, for assurance, including calibration and header checking; then transmitter and receiver data are merged and microseismic data is separated; Finally, data analysis and processing follows. LOTEM processing leads to inversion or in the FSEM case 3D modeling. Various 3D models verify the sensitivity under the salt dome. In addition, the processing was conducted pre-stack, stack, and post-stack. After pre-stacking, the noise was reduced, but showed the ringing effect due to a low-pass filter. Stacking and post-stacking with applying recursive average could reduce the Gibbs effect and produce smooth data

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-65095 (URN)10.1063/1.4990893 (DOI)000413696500007 ()2-s2.0-85026548327 (Scopus ID)
Conference
1st International Geo-Electromagnetic Workshop 2017, IGeo-EM 2017, Campus of Institute Technology of BandungBandung, West Java, Indonesia, 21-24 February 2017
Note

2017-08-15 (andbra);Konferensartikel i tidskrift

Available from: 2017-08-15 Created: 2017-08-15 Last updated: 2017-12-20Bibliographically approved
Beka, T. I., Senger, K., Autio, U. A., Smirnov, M. & Birkelund, Y. (2017). Integrated electromagnetic data investigation of a Mesozoic CO2 storage target reservoir-cap-rock succession, Svalbard. Journal of Applied Geophysics, 136, 417-430
Open this publication in new window or tab >>Integrated electromagnetic data investigation of a Mesozoic CO2 storage target reservoir-cap-rock succession, Svalbard
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2017 (English)In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 136, p. 417-430Article in journal (Refereed) Published
Abstract [en]

Recently acquired time-domain electromagnetic (TEM) and magnetotelluric (MT) data sets are utilized in the first electromagnetic (EM) characterization of a geological CO2 storage target site in Adventdalen, Arctic Norway. Combining the two EM data sets enabled to resolve the electrical resistivity structure of the target site better than either of the methods alone. 2D inverting the MT data in the audio period interval (0.003–1 s) with supporting input derived from the TEM data (0.01–10 ms) provided a geologically meaningful resistivity model that included information not previously evident from existing seismic and borehole data. The ca. 1.8 × 1 km 2D resistivity model displays a laterally constrained highly conductive anomaly (ca. 10 Ω m) at about 400–500 m depth, where reflectors of a parallel seismic section are concealed and core samples indicate a highly fractured décollement zone formed during Paleogene compression. The base of the permafrost is imaged at ca. 200 m depth. Synthetic inversion tests, however, suggest that this may be exaggerated by tens of meters, due to a thin conductive layer present approximately between 10 and 25 m depth. The resistivity model does not give indication for a fluid pathway we can connect to leakage, in line with water injection and leak-off tests in the reservoir and cap-rock, both of which indicate a sealing shale-dominated cap-rock separating an over-pressured compartment above the sealing shale from a severely under-pressured reservoir interval. The results we present indicate the advantage of integrating EM exploration techniques in a CO2 reservoir-cap-rock study to obtain a more complete picture.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-60720 (URN)10.1016/j.jappgeo.2016.11.021 (DOI)000392769700036 ()2-s2.0-84999861929 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2016-12-19 (andbra)

Available from: 2016-11-28 Created: 2016-11-28 Last updated: 2018-09-13Bibliographically approved
Beka, T. I., Smirnov, M., Birkelund, Y., Senger, K. & Bergh, S. G. (2016). Analysis and 3D inversion of magnetotelluric crooked profile data from central Svalbard for geothermal application (ed.). Tectonophysics, 686, 98-115
Open this publication in new window or tab >>Analysis and 3D inversion of magnetotelluric crooked profile data from central Svalbard for geothermal application
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2016 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 686, p. 98-115Article in journal (Refereed) Published
Abstract [en]

Broadband (0.001–1000 s) magnetotelluric (MT) data along a crooked profile collected to investigate the geothermal potential on Spitsbergen could not be fully explained by two-dimensional (2D) models; hence we interpret the data with three-dimensional (3D) inversion herein. To better accommodate 3D features and nearby off profile resistivity structures, the full MT impedance tensor data together with the tipper were inverted. As a model control, a detailed bathymetry is systematically incorporated in the inversion. Our results from testing different inversion settings emphasised that appropriately choosing and tuning the starting model, data error floor and the model regularization together are crucial to obtain optimum benefit from MT field data. Through the 3D inversion, we reproduced out of quadrant impedance components and obtained an overall satisfactory data fit (RMS = 1.05). The final 3D resistivity model displays a complex geology of the near surface region (< 1.5 km), which suggests fractures, localized and regional fault systems and igneous intrusions in the Mesozoic platform cover deposits. The Billefjorden fault zone is revealed as a consistent and deep rooted (> 2 km) conductive anomaly, confirming the regional nature of the fault. The fault zone is positioned between two uplifted basement blocks (> 1000 Ωm) of presumably pre-Devonian (Caledonian) metamorphic rocks, and the fault may have been responsible for deformation in the overlying Paleozoic-Mesozoic unit. Upper crustal conductive anomalies (< 10 Ωm) below the Paleozoic-Mesozoic succession in the western part of the 3D model are interpreted as part of a Devonian basin fill. These conductors are laterally and vertically bounded by resistive rocks, suggesting a conducive environment for deep geothermal heat storage. Having this scenario in an area of a known high heat-flow, deep faults and a thinned lithosphere makes the hypothesis on finding a technologically exploitable geothermal resource close to human settlement in the area stronger.

National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-12158 (URN)10.1016/j.tecto.2016.07.024 (DOI)000383303600008 ()2-s2.0-84983045036 (Scopus ID)b3cbb46c-242d-4789-bebd-891d707295d4 (Local ID)b3cbb46c-242d-4789-bebd-891d707295d4 (Archive number)b3cbb46c-242d-4789-bebd-891d707295d4 (OAI)
Note

Validerad;2016;Nivå 2;2016-10-14 (inah)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Autio, U., Smirnov, M., Savvaidis, A. S., Suopios, P. & Bastani, M. (2016). Combining electromagnetic measurements in the Mygdonian sedimentary basin, Greece. Journal of Applied Geophysics, 135, 261-269
Open this publication in new window or tab >>Combining electromagnetic measurements in the Mygdonian sedimentary basin, Greece
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2016 (English)In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 135, p. 261-269Article in journal (Refereed) Published
Abstract [en]

We present a novel approach where time-domain electromagnetic (TEM) data are transformed and subsequently used in two-dimensional (2-D) magnetotelluric inversion of the determinant of the impedance tensor. The main idea is to integrate TEM with magnetotelluric (MT) data to produce subsurface electrical resistivity models. Specifically, we show that 2-D MT data inversion of the determinant of the impedance tensor supported by inclusion of TEM–MT-transformed data has superior resolution at the near surface and at the same time static shift afflicting the MT data can be addressed. Thus, the approach allows for practical express integration of TEM data with MT measurements as opposed to a full combined 3-D inversion, which requires significant resources. The approach is successfully applied in the Mygdonian sedimentary basin located in Northern Greece. In addition to TEM and MT data, also controlled source — and radiomagnetotelluric data are available from the Mygdonian basin, which have been subjected to 2-D analysis previously. We have extended the analysis to a full 3-D inversion using ModEM code. All obtained models are analysed and are in a good agreement.

National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-60003 (URN)10.1016/j.jappgeo.2016.10.014 (DOI)000390731900025 ()2-s2.0-84993126391 (Scopus ID)
Note

Validerad; 2016; Nivå 2; 2016-11-20 (andbra)

Available from: 2016-10-27 Created: 2016-10-27 Last updated: 2018-07-10Bibliographically approved
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